Developers with projects above the airport-railway stations in Central and Tai Kok Tsui are taking advantage of a relaxation in government regulations to enlarge the usable area of their projects. Sun Hung Kai Properties, a shareholder in the consortium developing the Hong Kong Station project in Central, said the consortium would benefit from changes in the way the Buildings Department calculated gross floor area. A spokesman said the amount of extra space gained was not yet known and it had not been finalised whether the increase in gross floor area would result in a significant change in design. The consortium also includes Henderson Land Development, Hong Kong and China Gas and Bank of China Group. The department recently said it was prepared to accept the outer face of the structural elements in a curtain-wall system - such as beams, columns and floor slabs - as the external wall for the purpose of measurement of gross floor area. Some architects said the change would add about 2 per cent to the usable area of a curtain-wall building. The enlargement in plot ratio would lower slightly the average development cost of the projects which were under construction, they said. All commercial projects that had began construction in the past 12 months could benefit from the change in the calculation of gross floor area, they said. Kerry Properties, which has a 20 per cent in the first phase of the Olympic Station property development in Tai Kok Tsui, said the consortium would achieve a higher gross floor area in the commercial building that is under construction in site C. Executive director Steven Ho said three other office buildings in site A, which was sold to Hongkong Bank for $4.04 billion earlier this year, would not benefit, because those towers had been completed. Because of the gross floor area relaxation, Hutchison Whampoa reportedly is able to build two extra floors on its Cheung Kong Center in Central. Cheung Kong (Holdings) also is planning to enlarge the gross floor area of its commercial development in North Point. Cheung Kong Real Estate director Justin Chiu previously said Cheung Kong had no intention of having extra floor space in its project, The Center, because it was almost completed and the company did not want to change the design.